System of mining



Jan. 15, 1929. 1,699,098

w. M. DAKE ET AL sYs'rEu 0F mum Filed Aug. 16, 1923 4 Sheets-Sheet 2 VVlferMDak Rqymoncl 1/7- Fla lie;

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flttouiu Sheets-Sheet 5 W. M. DAKE ETAL SYSTEM OF MINING Filed Aug. 16, 1925 5,

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w. M. DAKE ETAL SYSTBI OF IINING 816. 1923 4 Sheets-Sheet 4 N n dltenMLDaEe Filed A? Patented Jan. 15, 1929.

UNITED STATES PATENT OFFICE.

"WALTER M. DAKE AND RAYMOND A. WALTER, OF WASHINGTON, DISTRICT 01' CO- LUMBIA, ASSIGNORS F ONE-FIFTH TO HARRY H. SEMMES, OF WASHINGTON, DIS

TRICT OF COLUMBIA.

SYSTEM 01 MINING.

Application filed August 16, 1923. Serial No. 857,714.

Our invention relates to methods and apparatus for mining, and while it is intended that it be employed in mining or recovery of any type of material, it is particularly adaptable to the mining of coal.

An object of our invention is to provide a system which is adaptable to both the Room and Pillar and the Longwall methods; of mining, or any modification or combina 10.tion of these two methods.

Another object of our, invention is to eliminate the use of mining cars and tracks,

as Well as rope haulage methods.

A further object of our invention is to eliminate high air pressure lines, or exposed electric wires, with their accompanying dangers and costs of installation.

Another object of our invention is to provide a complete automatic system for removal of material from mines, with an electrically controlled safety system in connection therewith, that permits shut-down ofthat portion of the mine within which the temporary disability occurs, without necessitating shutting down the entire system.

A further object of our invention isto provide a system which can'be easily and quickly installed at low cost, and yet WlllCh is sturdy and of-great mechanical strength.

A still further object of our invention is to provide a system in which the actual mining operation and transportation may be continued, even though the preparation or loading operation at the mouth of the mine may be shut down for considerable periods of time.

Yet another object .of our invention is to provide a. system which Will allow of speedy progress in the work,.thereby eliminating the danger of dropping roof material and subsequent loss of coal incident to the old type of mining, Wherethe excavations would necessarily stand for a much longer period of-time.

With these and other objects in view which may be incident to our improvements, the invention consists in the parts and combinations to be hereinafter set forth and claimed, with the understanding that the several necessary elements comprising our invention, may be varied in construction, proportions and arrangement without departing from the spirit and scope of the appended claims.

In order to make our invention more clearly understood, we have shown in the accompanying drawings means for. carry mg the same into practical efi'ect, without limiting the improvements in their useful applications to the particular constructions, WlllCll for the purpose of explanation, have been made the subject of illustration.

In coal mining it is customary to drive an adit or adits into the coal, either from 1t s outcrop, or from the shaft or opening giving access to the coal. Secondary passageways are driven to the right and left from these adits, and workin chambers are driven to the right and left from these pas sageways. It is from these working chamhers that most of the product is mined. This type of mining is called the Room and Pillar method. At times another method known as the Longwallmethod is employed, in which large blocks of coal several hundred feet wide are mined. I

In the system most commonly used, it is customary to remove the product from the mlne in cars or tubs running on tracks. These vehicles are pushed or ulled by man or animal power, or propel ed by air or electricity. At times ropes are used to haul the cars. This common systememploying tracks is very expensive in construction, and

v in operation, because of'the necessarydelayv so in switching. Great delay is also caused in changing loaded and empty cars at the faces. Baretrolley wires carrying electricity are a constant source of danger, as well as are pipe lines carrying compressed air, since these latter may blow outand injure the laborers. The service afforded by the track method of mine transportation is veig irregular and slow, adds greatly to the di culties and cost of conducting mining operations, and is a continual factor production.

The coal or material mined is usually loaded into cars or tubs at the face of the working chambers, thence it is hauled over 1 all repeated many times until the material mined reaches the outside. This frequent transfer of material results in excessive loss due to spillage and breakage, and is therefore commercially impracticable.

The automatic control systems, for such types of conveyors as justdescribed, provide forthe shut-down of all of the units should it become dangerous or impossible to operate any of them. This has meant the tie up of the entire system While repairs may be made to possibly only one of the units in the chain.

in whatever system employed, theoperationhas heretoforebeen limited by the ability of the preparation or loading plant to handle thematerial mined. Under certain conditions of operation, the minecars may be used to store a certain amount of the material, but the utilization of this costly 'equipmentfor such purposes is very uneconomical.

it is to overcome the disadvantages of the present systems of mining that this invention was conceived.

Tn the drawings Figure 1 is a diagrammatic sectional plan view of a mine with our system installed therein;

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Fig. 1 is a detail view in side elevation of the distributing. conveyor taken between the lines 1 and 1 of Fig. 1;

Fig. 2 is a longitudinal sectional View showing the application of our invention to a mine employing a shaft and skip;

3 is an enlarged diagrammatic view showing the operation of a loading machine and room conveyor in the mine room;

Fig. i is a detail side elevation showing the conveyor frame construction, anchoring means and stop contacts;

Fig. 5 is a diagrammatic illustration of a conveyor control system embodying our invention and employing direct current;

Fig. 6 is a diagrammatic illustration of a conveyor control system embodying our invention and employing three phase alternating current.

tlur system comprises the use of interlocking permanent conveyors automatically controlled, so that material mined may be delivered. from the working face directly onto a conveyor, and carried by the conpanacea veyor system straight to the mouth of the mine, without any further handling, and without subjecting the material to any undue breakage or loss. The conveyors are suitably anchored to floor, roof or sides, as conditions require, by a simple, inexpensive but firm anchoring construction, which can be installed at relatively low cost. The framework of the conveyor itself is made of extensible units.

At the mouth of the mine is provided a general storage bin into which conveyors can deliver the material mined. The general bin provides a reserve reservoir which can be filled by a continuous mining operation, and from which the material to be treated can be drawn as necessity requires, without necessitating spasmodic operation of the mine in order to supply material only when the treating apparatus can conveniently care for it. In conjunction with our continuous conveyors, we have a control system which eliminates the danger of operation of any of the conveyor equipment under unfavorable conditions, but which shuts down only the poytion of the system between the apparatus in such dangerous condition and the face of the mine. This permits the remainder of the mine to be operated at full capacity, while repairs or adjustments are made to that portion shut down.

Referring to the drawings for a detailed description, Fig. 1 shows a mine having a main adit 1. Adjacent the main adit l is an air passage 2 having branch air passages 3 communicating therewith. Cour municating with the main adit 1 is a branch adit 4, and parallel therewith is an air passage 5. The-air passage 5 connects with the branch adit 4 by means of connecting passages 6. Leading into the main adit l is another branch adit 7.

Leading into the branch adit 4 are rooms 8, 9 and 10. Air passages 11 join these roomsr This general mine plan described is merely representative of any of the usual types of Room and Pillar mine workings. it is ob vious that in place of the rooms the Longwall type of mining may be employed, and hereafter when the word room is referred to, it is to be understood that it means any working place. It is obvious that these passageways may be either horizontal or at any natural angle. Operating in the main adit l is an extensible permanent conveyor 12, which is diagrammatically illustrated. The conveyor 12 is adapted to run on idlcrs l3, and the direction of travel of the top of the conveyor is normally in the direction of the arrows, but may be reversed to transport supplies in the mine. The main line conveyor 12 is adapted to be driven by a motor 14 through a standard driving mechanism 15.

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In the branch adit 4 is adapted to travel a permanent extensible conveyor 16 which travels on idlers 17. The direction of travel of the upper face of the branch line conveyor 16 is indicated by the arrows, but it may be reversed in the same way as conveyor 1:2. The branch line conveyor 16 is driven by a motor 18 through adrivingr connection 19. The conveyor 16 is adaptedto discharge into a chute 20, which is adapted to deliver material on to the main line conveyor 12. a

lVithin the branch adit 7 is a pe manent extensible conveyor 21, adapted to be driven by a motor 22, through a driving connection -The direction of travel of the upper surface of the permanent extensible conveyor 21 is in the direction of the arrow; this too may be reversed in the same manner as conveyor 12. The conveyor 21 travels over idlersQl and delivers into a chute 25, whose end projects over the main line conveyor 12, and which is adapted to deliver material on to the main line conveyor.

In the rooms are portable extensiblev conveyors 26. A similar portable extensible conveyor 26 is shown discharging} 011 to the branch line conveyor 16, at a point near the junction of the branch line conveyor 16 "with the main line conveyor 12. The port able extensible conveyors 26 are adapted to be driven by motors 27, through suitable drive mechanisms 28.: The direction of travel of material on the portable extensible conveyors 26is indicated by the arrows.

These conveyors may be reversed to transport supplies to the Working faces.

In room 8 We have shown a standard load ing machine 29 delivering material 31 which has been loosened, on toportable extensible conveyor 26.

For purposes of clearness, We have illus trated only one loading machine operating,

though there may be loading machines operating in each room of the mine, or the mate rial may be loaded on to the conveyor 26 by hand, or other suitable means.

Referring to Fig. 8, We have shown a loading machine operating in room 8 in greater detail. It is customary to have supporting props 32 for supporting the roof adjacent to the portable extensible conveyor 26. to prevent injury to the conveyor by falling of the roof. F or purposes of clearn'ess, We have diagrannuatically illustrated an undercutting machine 33 operating on the working facebst, cutting a slot or undercut In operation the slot or undercut is extended across face 34 and then the material is blasteddorvn. and the loading machine operates on theyfallen material.

The main line permanent extensible conveyor 12 is adapted to deliver the material on to a distributing conveyor 36. The distributing conveyor 36 is driven by a motor indicated by the arrow.

37, through suitable drive connections 38, .-.nd the direction of travel of the upper surface of the distributing conveyor 36 1s Referring to Fig, it for detail, the cork struction of such a distributing conveyor is more clearly shown. A permanent belt coin veyor 36 travels around an upper roller '35) and around a lower roller dlgboth suitably journaled in a traveling "frame 42. The frame 42 is mounted on rollers 43, nhich travel on tracks 14 positioned above a reservoir storage receptacle or bin 45. The reservoir storage receptacle may bedivided into compartments by dividing ivalls 46 it do: fiill'fid i v; i i

The material carried on the uppersurface of the distributing conveyor 36 passes down into a chute 47, and is .delivereth as indicated by the arrows in Fig. 1 into the reservoir storage receptacle 45. The-particular portion of the reservoirinto which the distributing conveyor 36 discharges the material can be regulated, by moving the frame 42 so that the chute 47 occupies a desired position above the reservoir 45.. Each cont partment in the reservoir: ao'has suitable discharge gates 48, through whichmatcrial can be discharged at will on toa reclaiming conveyor 49, which latter-tisadapted to deliver the material to railroad carsortothe preparation plant, such as. atippleh-inthc case of coal, or to anyothndesired destina-' tion. I e 4w The reservoir storage receptacle 45 per- Inits the continuous operation. ofthemine, since the mining operation ClOGSuDOt have to be held up to await the preparation of the material. This reservoir storagebin operates as an equalizing reservoir. between the mine andthe preparation or loading plant. Should it be necessary at times to shut down the mine for repairs, or for cleaning of Waste material, or other neces sary Work; the reservoir storage bin can be drawn onby the preparation plant -or by the railroad cars, and no time is lost. This equalizing function will prevent a large portion of the economic Waste attendantto the present systems of operation;

Though the main line' conveyor .12 is adapted to discharge, ordinarily, on to the distributingrcouveyor so, to dispose of waste from the mine. We have provided at the end of the main line conveyor a movable chute 51, diagrammatically illustrated, which can deliver the material to; a waste con 'eyor 52. The waste conveyor 52 and the connections necessaryto dischargematerialthereon, may be located at any place along the main line conveyor or a branch line conveyor, as is found convenient or necessary in practice.

In Fig. 2 we have shown a system in which the main line conveyor 12 is adapted to discharge into a shaft pocket 53. The

shaft pocket 53 has a downwardly sloping wall 54 and a discharge gate 55. A mine of this type is provided with a shaft 56 in which is adapted to travel a skip 57 for hoisting the material mined to the surface. The skip 57 is hoisted by means of a hoist rope 58, passing over a sheave 59 supported above the shaft on framework 61. The hoist rope 58 is attached to the top of the skip, and the side of the skip is provided with outstanding projections 62 which slide on guides 63. Only one ofthe guides 63 is shown by reason of the fact that in the drawing the guide on the far side of the car is hidden by the guide on the near side.

' At the mouth of the mine there is provided a storage bin 64 having a discharge gate 65 in its'bottom, from which material delivered into the bin may be discharged upon the conveyor 66 traveling in the direction of the arrow, and carried to a loading or preparabin 64. Any delay in operation of skip 57 is equalized by the storage capacity of shaft pocket .53, permitting continuous operation of belt 12.

It is contemplated that in some contingencies the main and branch line conveyors will operate at an angle instead of in the horizontal plane. These conveyors may be operated conveniently up to the angle at which the material will repose on the moving conveyor without slippage .or spillage. In some instances it, may be necessary to employ horizontal conveyors, in combination with conveyors working at a vertical angle, and to also employ the skip and shaft method. The skip may work at any angle,between the angle of respose of material on the moving conveyor, and the vertical.

Referring to Figs. 2 and 4, the conveyor '12 is. shown as supported by the idlers 13 which are journaled on idler frames 67. The outside idlers 13 are set on the frame so that their axis lies obliquely and upwardly inclined from the horizontal, which causes the belt 12 to present a concave upper surface. This prevents 'spillageof material to a large extent. The belt passes over a pulley wheel 68 which is rotated by means of a motor through a suitable transmission mechanism. In the case of the belt 12, the motor 14 operating through transmission mechanism 15, rotates the pulley 68. and causes; the belt to travel. The belt on its return is adapted to lie fiat and passes over a series of idlers 69, which we have shown in this case as mounted on a supporting frame 71 in suitable bearings 72.

Upon breakage of the conveyor belt 12, the belt, which is formed of some suitable flexible material as canvas and rubber, will fall and will push against the flexible contact arm 7 3, causing the contact arm 73 to flex downwardly and make a contact with the contact 74c. The contact arm 73 is electrically connected to a binding post 75, and the contact arm 7 3 and the binding post 75 are fastened to and electrically insulated from the supporting framework 71. The contact 7 4 is electrically connected to a binding post 76, which is also electrically insulated fromand attached to the supporting framework 71. The breakage of a belt, therefore, closes a circuit through binding post 75 and binding post 76 and through the control s stem, as will later be more fully set fort 1.

In Fig 5 we have shown a direct current control system for use with our system of conveyors. Where we employ electric motors to drive the conveyors, we may use direct current, which is fed in through power lines 200 and 201. lVhile We prefer to employ all wires insulated, it, of course, is obvious that where such is not practicable, bare wires may be used. The main.power leads 200 and 201 supply power for the main electric motor 14 of our main line conveyor. Branch power lines 202 and 203 supply power to the branch line motors and the room motors. For the purpose of simplicity of description, we have shown but one branch line conveyor motor 18 and one room conveyor motor 27.

In the main. power line we have located a master switch 204, normally held closed by means of a spring 205. Conneted to the master switch 204 is a solenoid core 206. Power is delivered to the main line conveyor motor 14 through leads 207 and 208. The motor 14 drives the main line conveyor belt 12, as has been previously described. As' has been above set forth, uperbrcakage of the conveyor belt 12, the lower portion of the belt will fall and cause flexible contact 73 to touch contact 74. In Fig. 5 the belt and contacts are diagrammatically illustrated for purposes of clarity in explanation.- The touching of COl'ltEl-t ts 73 and 74, closes the circuit throughlead 209 to main 200, at the same time a circuit is likewise completed through lead 211, through solenoid winding 212, and lead 213, to main 201.

When the belt 12 breaks and the circuits are completed as deseribed, current flows- .through solenoid winding 212, and solenoid 206 is attracted against the force of spring 205 to open the circuit inthe main line. This causes motor 14 to stop, and cuts off 200 and 201 remains closed. However, upon overload of the circuit, an excessive amount a of current flows through tlip shunt circuit including the solenoid winding 217, and the encrgization of the solenoid Winding 217,

is sufficient to overcome the tension of the spring 205 and attract the solenoid core. A locking device (not shown) of the cus tomary type holds the switci 204 in the open position until the condition can be In the lead 207 of the motor islocated a resistance device 218 and across the resistance device 218 is shunted a solenoid winding 219, through leads 221 and 222. Overload of the motoi" 14, or short circuiting 1n the motor, will cause an excessive amount of current to flow through the solenoid winding 219 and switch 204 will be opened.

Under normal conditions there is not enough 'current flowin through the solenoid winding 219 and t e solenoid winding 217, for their additive force to be sufficient to 0 en the switch 204. However, upon overloa of the motor, solenoid winding 219 will attract the solenoid and open the switch. The holding device (not shown) will retain the switch in open position until the abnormal, condition can be rectified.

To sum up, breakage of the main conveyor belt, overload of the main circuit,

l5 .line, stopping the main conveyor, all branch or overload or short circuiting in the main conveyor motor 14 will open the main power line conveyors and the room conveyors.

Inthe branch power line comprising the leads 202 and 203, is located aswitch 223 'ilarly located under the belt of the con- 'veyor.v Upon breakage of the branch line conveyor belt 16, the lower portion of the normally held closed by means of a spring 224. Connected to the branch "line switch 223 is a solenoid core 225. Power is delivered to the branch line conveyor motor 18 throughleads 226 and 227. The motor 18 drives the branch conve or belt 16. I The branch conveyor' belt '16 as a flexible conv tact arm 228 similar to the flexible contact arm 73 of the main line conveyor, and simbelt will fall and cause flexible contact 228 to touch contact 229. Closing of the cir cuit between the flexible contact 228 and contact 229, completes the circuit through lead 230 to main lead 200. At the same time a circuit is likewise completed through lead 231, through a solenoid winding 232, and lead 233 to main lead 201.

In the circuit as described, upon breaking of the belt 16, current flows through solenoid winding 232, and solenoid core 225 is attracted against the force of spring 224 to open the circuit in the branch line. The motor 18 then stops and since all current is cut off in that branch line, all room motors in the entire system of that branch line are stopped.

a In branch line 203 is'inserted a resistance element 233 and shunted across the ends of the resistance element, by means of leads 235 and 236, is a solenoidwinding 234. Normally, the current flowing through the shunt circuit connected to either side of the resist-ance 233 is not suflicient toovercome the action of spring 224. Upon overload of the branch circuit, however, an excessive amount of current flows through the shunt circuit, and the energization of the solenoid winding 234 is suflicient to overcome the tension of the spring 224 which attracts the solenoid core. A locking deviceof the customary type (not shown) is adapted to. hold the switch 223 in the open position, untilvnormal conditions have returned, at which time the latch can, be released.

In the lead 227 of the motor'is located a resistance device 237, and across said device A is shunted a solenoid winding 238, through.

leads 239 .and 241. Upon short circuiting of the motor 18, or overload'in the motor circuit, an excessive-amountof current will flow through the solenoid winding 238, which will attract the against thetension of the spring 224 and open switch 223. The switch will be re tained in the open device (not shown).

It is to be understood that ordinarily there is not enough current flowing through the solenoid winding 238 and the solenoid winding 234 together to open the switch 223.

Upon overloading of the branch circuit, or upon. overloading'or short circuiting of the motor, however, either one of. the solenoid windings aflected by such conditions will be sufficient alone to open switch 223.

Theroom conveyor motor 27 is connected solenoid core 225 to the branch line leads 202 and 203, by

leads 242 and 243, respectively. A switc 244; which is normally held closed by a spring 245,has attached thereto a solenoid core 246. In the lead 243 to the motor is positioned a resistance device 247, and shunted around the resistance device is a solenoid winding 248, which is connected to said resistance deviceby leads 249 and 251. Should the room conveyor 27 be short circuited, or overloaded, the amount of current flowing through the solenoid core 248 will be suflicient to overcome the tension of 105 position by a locking ill till

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the spring 245 and open the switch 244. A suitable locking device (not shown) holds such switch open until the dangerous condition can be rectified. Under ordinary conditions, however, the amount of current flowing through the solenoid winding 248 is not sutiicient to overcome the tension of the spring 245, and the circuit remains closed.

in the system which we have devised, all branch line and room conveyor circuits will be made dead upon breakage of the conveyor belt of the main line conveyor, or'upon OXQY- load or short circuiting of the main line motor, or upon overload of the main line cir- Should there be an overload in'the branch line, or'should the branch line con-' veyor belt break, or the branch line motor become short'circuited or overloaded, the circuits in the branch line, including all room conveyorcircuits feed from such branch line will be rendered dead, but the main line and other branch lines in which dangerous condition does not exist, will continue to opcrate. Dangerous condition in the room conveyor motor, stops the room conveyor motor only.

in Fig. 6 is shown our control s stern as adapted to a three-phase source 0 supply. lhe power is deliveredto the various motors in the system b means of three-phase power niains having eads 252, 253 and 254. The

solenoid winding 212, which operates the solenoid 206 upon breakage of the main conveyor belt, is connected across leads 252 and 253 and is in fact a potential'coil. Upon breakage of the belt, the solenoid 206 is attracted against the tension of the spring to open switch 204.

The solenoid winding 217' is connected in series with current transformers 55, which are themselves connected in series and inductively related to mains 252 and 253 of the main 'power line; Upon overload of the main line circuit, solenoid winding 217 will cause opening of the master switch 204 and shut down all motors. The same result will be accomplished upon failure of any phase, since the excessive current generated in the solenoid winding 217, will open the master switch. The solenoid winding 219 is connected in circuit with current transformers 256 which are connected in series and inductively associated with two of three leads in the motor circuit. llpon short circuiting of the motor, or overload of the motor, or-failure of one of the phases in the motor circuit, the ex cessive current-generated in the solenoid winding 219 will operate to open the switch 204.

Provision is made, as in the direct current system, for keeping the switch open until repair has been made. As in the direct current system, the added attractive force of r been again established.

solenoid windings 217' and 219' are not suf ficient to open the switch under normal conditions, but either one alone will open the switch upon the occurrence of abnormal conditions, as above set forth:

The three-phase branch power line comprising the leads 257, 258 and 259 supplies power to the branch line conveyor motor 18, and the room conveyor motors 27.

Upon breaking of the belt 16, circuit is closed through solenoid winding 232, which operates as a potential coil and is connected between leads 252 and 253 of the main power line. Solenoid core 225 is then attracted to open the switch 223 against the tension of spring 224, and shut off power to the branch line conveyor motor 18, and all room conveyor motors operating conveyors feeding that branch line conveyor.

Solenoid winding 234 is connected in series with current transformers 261 which are connected in series and inductively associated with leads 258 and 259 of the branch power line. Upon overload of the branch line circuit, or failure of a phase, the increased current in solenoid Winding 234,

causes the solenoid core 225 to be attractedto open the switch 223 against the tension of spring 224.

The solenoid winding 238 is connected in series with current transformers 262., The current transformers are connected in series and inductively associated with two 'of the leads in the three phase motor circuit, of the motor 18. Upon failure of phase in the motor circuit, short circuiting or overloading, the excessive current induced in the solenoid winding 238' will attract the solenoid 225 to open the switch 223 against the tension of the spring 224.

The normal attractive force of the solenoid windings 234 and 238 are not sufiicient together to open the-switch 223, but either one alone, under abnormal conditions above set forth, will open the switch 223, thereby cutting off the current to the branch line motor, and to all room conveyor motors feeding on to the branch line conveyor. A. suitable latch device (not shown) will hold the switch open until the abnormal conditions can be rectified.

\Ve have shown inductively associated with two of the three leads to the room motor 27 current transformers 263 which are connected in series. Connected in series with the current transformers 263 is a solenoid winding 248.- Upon overload of the conveyor motor circuit, or short circuit\ ing, or failure of phase, the excessive amount of current flowing through solenoid winding 248 will cause the switch 244 to open, and a suitable latch device will hold it open until conditions for Under normal conper operation have ditions, however, the attractive force of the solenoid winding 248 will not besufiicient to open the switch.

Tosum up, in the three-phase system just rial by mining, having in combination main' described, the main line circuit switch will be opened, thus cutting off power to all branch line motor and room conveyor motors, upon breakage of the main conveyor belt, upon overload of the main line circuit, or failure of phase, or upon overload, failure of phase or shortcircuiting of the main line motor. The branch line circuit Will be opened upon breakage of the branch line conveyor belt, upon overload, or failure of phase in the branch line circuit, or upon overload, failure of phase, or short circuit; ing in the branch line motor circuit. When a branch line motor fails, all power to the room conveyor motors which operate conveyors feeding to the branch lineconveyor will .be stopped. However, opening of a branch line circuit does not afi'ect operation of the main line conveyor, or of the other branch line conveyors and their room con 'vevors. Upon short circuiting, overload or failure of phase in a room conveyor motor, the room conveyor circuit is opened. lVhen such takes place, no other room motors are affected, nor is the operation of any branch line or of the main line conveyors stopped.

While we have shown and described the I preferred embodiment of our invention, we

wish it to be understood that we do not confine ourselves to the precise details of construction herein set forth, by way of illustration, as it is apparent that many changes and variations may be made therein, by

those skilled in the art, without departing from the spirit of the invention, orexceeding the scopeof the appended claims.

We claim Y 1. Apparatus for the removal of material by mining having in combination main and branch'line conveyors; means operative to stop the main and branch lines upondan gerous condition. in the main, line; and means operative to stop a branch line conveyor only upon dangerous condition in that branch line. 1 y

2. Apparatus for the removal of material by mining having in combination main,

branch and room conveyors; means operative to stop the main, branch and room'conveyors upon dangerous condition in the main line; and means operative to stop a branch line and its room conveyors only upon dangerous condition. in that branch line.

3. Apparatus for the removal of material by mining, having in combination main,

branch and room conveyors'; means operative to stop the main, branch and room conveyors upon dangerous condition in the main line; means operative to stop 'a branch line and its room conveyors only upon dangerous condition in that branch line; and

unit.

10. Apparatus for the, removalof mate- 'means operative to stop a room conveyor only upon dangerous condition in that room conveyor.

4. Apparatus for the removalof mate,-

by mining, having in combination main,,

branch and room conveyors; means operative to stop the main, branch and room con-' veyoi's upon breakage of the main line conveyor; and means operative to stop a branch line and its room conveyors upon breakage -of that branch line conveyor.

6. Apparatus for the reniovalof material by mining, having in combination main, branch and room conveyors; means operative to stop the main, branch and room conveyors upon breakage of the main line conveyor; means operativeto stop a branch line and its room conveyors only upon breakage of that branch line conveyor; and

means operative'to stop a room conveyor only upon dangerous condition in the room conveyor.

7. Apparatus for the removal of material by mining, having in combination main and branch line conveyors; separate power units for each of the conveyors; means operative to stop the main and branch line conveyors upon dangerous condition in the main. line power unit; and means operative to stop a branch line conveyor only upon dangerous.

condition in that branch line power unit.

8, Apparatus for the removal of material by mining, having in combination main, branch and room conveyors; separate power units for each of the conveyors; means operative to stop the main, branch and room conveyors upon dangerous condition in the ,main line power unit; and means operative to stop a branch line and its room con veyors only upon dangerous condition in that branch line-power unit.

9. Apparatus for the removal of material by mining, having in combination maing branch and room conveyors; separate power units for each of the conveyors; means operative. to stopthe main, branch and room conveyors upon'dangerous condition in the main line power unit; means operative to stop a branch line and its room conveyors only upon dangerous condition in that branch line power unit; and means operative to stop a room conveyor only upon dangerous condition in the room, power rial by mining having in combination mainand branch line conveyors; separate motors for operating each conveyor; main line and branch line circuits for supplying thev motors; means operative to stop the main and branch hne motors upon overload on the main line circuit; and means 0 erative to stop the branch line motor 0 y upon overload on that branch line circuit.

11. Apparatus for the removal of material by mining, having in combination main, branch and room conveyors separate motors for operating each conveyor; main, branch and room circuits for supplying the motors, means operative to stop the main, branch and room motors upo'n overload of the main line circuit; and means operative to stopa branch and its room motors only upon overload of that branch line circuit.

are of a phase in the main line circuit; and

means operative to stop a branch line motor only upon failure of a phase in that branch line circuit. a v

r 13. Apparatus for the removal of material by mining, having in combination main, branch and room conveyors; separate motors for operating each conveyor; three phase main, branch and room circuits for supplying the motors; means operative to stop the main, branch and room motors upon failure of a phase in the main line circuit; and means operative to stop a branch line motor and its room motors only upon failure of a phase in that branch line circuit.

14. Apparatus for the removal of material by mining, having in combination main, branch and room conveyors; separate motors for operating. each conveyor; three phase main, branch and room circuits for supplying the motors; means operative to stop the main, branch and room motors upon failure of a phase in the main line'circuit; means operative to stop a branch line motor and its room motors only upon failure of a phase in that branch line circuit; and means operative to stop a room conveyor only upon dangerous condition in the room motor.

In testimony whereof We afiix our signatures.

- WALTER M. DAKE.

RAYMOND A. WALTER. 

